The invention in general relates to sonic fusion technology. In particular, the invention relates to an ultrasonic applicator as well as to a method of using the same. An exemplary use of an ultrasonic applicator according to the invention may be for augmenting a bone screw within a fractured bone.
U.S. Pat. No. 4,653,489 discloses a system wherein a fixation cement is introduced through a bone screw into a portion of a bone afflicted by osteoporosis. Femoral neck fractures as well as distal femoral fractures can be fixated by means of this system.
US 2007/0063618 discloses an ultrasonic transducer device, comprising an active piezo ceramic material that contains less than 2% lead, piezo materials with a low Curie temperature, a high compressive bias force applied to the piezo ceramic elements, a bias bold sub-assembly that includes a component assembled with a low-temperature glass-transition point filled epoxy material, and/or a permanently attached end effector with a self-locking taper.
The system in accordance with the prior art comprises a bone screw having a flow cavity, that is an axial through bore through which bone cement can be introduced into the portion of the tip of the screw. The bone cement is advanced by a device which is releasably attached to the trailing end of the screw. This device is similar to a commercially available syringe in comprising substantially a cylindrical barrel and a plunger. The barrel forms a cavity in which the plunger is movable to and fro.
In use of this prior art device, the fixation cement is filled into the barrel, after which the plunger is urged against the cement. By applying manual compression force, the fixation cement is jetted into the axial through bore of the bone screw. Due to the pressure, the fixation cement is adequately fluidized so that it can pass through the proximal end of the bone screw into the bone, as a result of which the bone screw is augmented in the bone.
This system has the drawback that the manual pressure applied to the fixation cement varies, not only basically from application to application but also during the application itself, so that the distribution of the fixation cement within the portion of the bone and the tip of the bone screw is neither reliable nor even.